The most sensitive part in a dental implant system is the fixture, i.e. that part of the system which is screwed or inserted into a hole in the jaw bone and which thus comes into direct contact with the tissues in the jaw. A suitable material for these implants is titanium. The use thereof as a material in surgical implants was suggested early (for instance by Leventhal et al in the Journal of Bone and Joint Surgery vol 33A, No 2, April 1951).
It is known that the fixture has to be very clean if the ingrowth of the bone tissue onto the implant, the so called osseointegration process, shall function in an optimal way. It even has been maintained that a contamination corresponding to a monomolecular layer could endanger the continued existence of the implant in the tissue.
The structure of the surface of the implant also is important.
The Swedish patent SE-C-416175 (7902035-0) for instance states that a better result of an implant operation is achieved if an implant with a surface of titanium oxide is provided with pores having a size of 10-1000 nm defined as being "micropits". This patent specification does however not clearly show how this surface differs from other known surfaces, for instance turned surfaces, or to what extent the retention of the implant is improved.
Several other publications have discussed the importance of the surface roughness for the retention of the implant, for instance the academic treatise by Jan Lundskog: "Heat and Bone Tissue" Laboratory of Experimental Biology, Department of Anatomy, University of Gothenburg, Sweden 1972, the article "Adhesion of bone to titanium", by S. G. Steinemann, J. Eulenberger, P.-A. Maeusli and A. Schroeder in Biological and Biomechanical Performance of Biomaterials, edited by P. Christel, A. Meunier and A. J. C. Lee, Elsevier Science Publishers B. V., Amsterdam 1986 and the article "Removal Torques for Polished and Rough Titanium Implants", Carlsson L., Rostlund T., Albrektsson B., Albrektsson T., Int J Oral Maxillofac Implants, 1988; 3:21-24. These publications indicate that it may be better with an implant surface having larger (macroscopic) irregularities or pores than those described in the above Swedish patent.
Implants have been made by cutting operations for a long time, primarily by turning. According to the above Swedish patent such a machining may result in a surface with microscopic irregularities. Several cleaning methods have been suggested and used, such as cleaning with organic solvents, electropolishing, sand blasting and treatment with alkalic and acid solutions.
One commonly used cleaning method thus is blasting with well known blasting agents, such as sand or aluminium oxide. Blasting with a blasting material having correctly sized particles results in the surface roughness which is desired in order to obtain a good mechanical retention in the bone. One problem with blasting the surface of the fixture is however that, although the existing contaminations may be removed, residues from the blasting agent may remain on the surface of the implant. The blasting agents commonly used, for instance aluminium oxide, thus may result in contaminations that are impossible or very difficult to remove in a subsequent cleaning process.